Impact of International Decisions on TAI Generation

Claudine Thomas

Abstract:	Under the terms of the Convention du Metre, the Bureau International des Poids et Mesures (BIPM) operates under the supervision of the Comite International des Poids et Mesures (CIPM). The CIPM has created a number of consultative committees which bring together the world's experts in their specified fields as advisers on scientific and technical matters. Among them, the Comite Consultatif pour la Definition de Seconde (CCDS) deals with the definition and realization of the second, and the establishment and diffusion of International Atomic Time (TAI) and Coordinated Universal Time (UTC). The CCDS held its 13th meeting in March 1996. It made a number of recommendations and addressed requests to its Working Groups, some of which have a direct impact on the work carried out at the BIPM Time Section. The most important recommendation is Recommendation S2 (1996), which concerns the application of the correction for the blackbody radiation shift to the results of all primary frequency standards. As this has direct consequences for the accuracy of TAI, immediate action was necessary. Another example is the creation of a CCDS Working Group on the expression of uncertainties in primary frequency standards. Evidence of the need for such a group became clear during discussion of how uncertainties should be presented and interpreted when combining measurements of the SI second produced by primary frequency standards. Finally, the Recommendation S4 (1996), which asks for coordination of the GPS and GLONASS timing systems, may lend to a worldwide network of time links using GPS and GLONASS in a complementary way. The aim of this paper is to present these international decisions to the timing community, to show how they influence the work of the BIPM Time Section, and to figure out the consequences for TAI.
Published in:	Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting December 3 - 5, 1996 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	25 - 36
Cite this article:	Thomas, Claudine, "Impact of International Decisions on TAI Generation," Proceedings of the 28th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 1996, pp. 25-36.
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